<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script>
alert(null==undefined);
alert(null===undefined);
var  s ="dd   dd";
s.len =8;
alert(s.len);
var aa = 'test string';   
           alert(typeof aa);  // 'string'   
           alert(typeof 90);  // 'number'
</script>
</head>

<body>
</body>
</html>
